Application of Different Testing Methods for Evaluating Effects of Hydrated Lime in Bituminous Mixes

AbstractHydrated lime has been known to be one of the most effective and durable additives in increasing moisture resistance of asphalt mixes. Indirect Tensile Strength (ITS) test is probably the most widely used testing method for evaluating moisture resistance of bituminous mixes. However, this determines resistance of mixes under certain testing conditions that may not be similar to field conditions. In this research, in addition to ITS, two other tests that are normally used for other testing purposes, have been adopted. These were Marshall and Wheel Tracking (WT) tests which are commonly used for mixing design and determination of deformation resistance of mixes respectively. Asphalt Concrete (AC) mix samples, containing various amounts of hydrated lime (ranging from 1 to 2%), were prepared and were compacted in both cylindrical and slab molds. The former samples were used for Marshall and ITS testing purposes and the latter samples were used for WT testing. The above tests were carried out, both at dry and wet conditions and at two different temperatures with the aim of evaluating moisture resistance and temperature susceptibility of mixes. The results indicated that the above testing methods are appropriate for evaluating moisture resistance of AC mixes

Evaluation of PFWD as potential quality control tool of pavement layers

Portable Falling Weight Deflectometer (PFWD) that can be considered as simple equipment is mainly used to measure elastic moduli of pavement unbound layers. This paper evaluates the potential use of PFWD to reliably measure the elastic modulus of pavement layers. To achieve this, PFWD tests were conducted on highway sections selected from different projects in Tehran. The California Bearing Ratio (CBR) laboratory tests were also conducted on samples collected during field tests. PFWD testing parameters were varied while performing the field testing. These included drop weight, drop height, plate diameter and position of additional geophones. In addition, PFWD moduli were compared with those obtained from performing FWD testing on the same site. It was found that drop mass and loading plate size affect PFWD modulus significantly. In addition, the results indicated that good correlation exist between PFWD moduli and FWD and CBR results. Santrauka Nešiojamasis krintančio svorio deflektometras PFWD (angl. portable falling weight deflectometer) yra nesudetingas prietaisas, dažniausiai naudojamas kelio dangu nesurištu sluoksniu tamprumo moduliui nustatyti. Straipsnyje apžvelgta, kaip PFWD naudojamas kelio dangu sluoksniu tamprumo moduliams matuoti. Taikant PFWD išbandyti skirtinguose projektuose Teherane (Iranas) panaudoti kelio dangu skerspjūviai. Bandiniams papildomai atlikti Kalifornijos santykinio atsparumo rodiklio CBR (angl. California bearing ratio) nustatymo eksperimentiniai tyrimai. Atliekant lauko tyrimus naudoti skirtingi PFWD bandymu parametrai: krintantis svoris, kritimo aukštis, plokštes skersmuo ir papildomai išdestyti geofonai. PFWD nustatyti tamprumo moduliai palyginti su tamprumo moduliais, išmatuotais naudojant krintančio svorio deflektometra FWD (angl. falling weight deflectometer). Nustatyta, kad PFWD matavimu rezultatams didele itaka turi kritimo mase ir apkrovimo plokštes matmenys. Gauti eksperimentiniu tyrimu rezultatai parode, kad PFWD, FWD ir CBR matavimai gerai koreliuoja tarpusavyje. Published Published Online: 24 Jun 2011 Reikšminiai žodžiai: kokybes kontrole, tamprumo modulis, nešiojamasis krintančio svorio deflektometras, Kalifornijos santykinis atsparumo rodikli

Application of FWD data in developing dynamic modulus master curves of in-service asphalt layers

This paper presents a simple method to determine dynamic modulus master curve of asphalt layers by con­ducting Falling Weight Deflectometer (FWD) for use in mechanistic-empirical rehabilitation. Ten new and rehabilitated in-service asphalt pavements with different physical characteristics were selected in Khuzestan and Kerman provinces in south of Iran. FWD testing was conducted on these pavements and core samples were taken. Witczak prediction model was used to predict dynamic modulus master curves from mix volumetric properties as well as the bitumen viscosity characteristics. Adjustments were made using FWD results and the in-situ dynamic modulus master curves were ob­tained. In order to evaluate the efficiency of the proposed method, the results were compared with those obtained by us­ing the developed procedure of the state-of-the-practice, Mechanistic-Empirical Pavement Design Guide (MEPDG). Re­sults showed the proposed method has several advantages over MEPDG including: (1) simplicity in directly constructing in-situ dynamic modulus master curve; (2) developing in-situ master curve in the same trend with the main predicted one; (3) covering the large differences between in-situ and predicted master curve in high frequencies; and (4) the value obtained for the in-situ dynamic modulus is the same as the value measured by the FWD for a corresponding frequency

Prediction of depth temperature of asphalt layers in hot climate area

In determination of flexible pavement layers moduli using Falling Weight Deflectometer (FWD), the pavement depth temperature should be determined and then the moduli should be corrected into a reference temperature. As direct measurement of pavement temperature is time consuming and is difficult to be determined in trafficked roads, some models are developed to predict temperature of asphalt layers through pavement depth, including BELLS model. The objective of this research is to determine correlation between actual measurement and prediction of temperature variations through asphalt layers with applying BELLS model. Ten new and rehabilitated pavement sites were selected in hot climate regions in Khuzestan and Kerman provinces in southern part of Iran. In typical hot summer days, pavement temperatures were measured at half and at one-third of the depth of asphalt layers and FWD testing were performed. Results indicated that a linear regression analysis of BELLS predicted temperatures versus measured values, provides very good correlation with actual field measurements of temperatures through the asphalt layers. Furthermore, predictions were more precise in rehabilitated pavements rather than in newly constructed pavements. Finally, using multi parametric linear fitting analysis, a new model was developed to accurately predict the temperature of asphalt layers in new pavements

A new method to determine maintenance and repair activities at network-level pavement management using falling weight deflectometer

Pavement condition assessment at network level requires structural evaluation that can be achieved using Falling Weight Deflectometer (FWD). Upon analysing FWD data, appropriate maintenance and repair methods (preser­vation, rehabilitation or reconstruction) could be assigned to various pavement sections. In this study, Structural Condi­tion Index (SCI), defined as the ratio of Effective Structural Number (SNeff) to Required Structural Number (SNreq), was used to determine if a pavement requires preservation or rehabilitation works (i.e. preservation SCI > 1, rehabilitation SCI < 1). In addition to FWD deflection data, SCI calculation requires pavement layer thicknesses that is obtained using GPR with elaborated and time consuming works. In order to reduce field data collection and analysis time at network-level pavement management, SCI values were calculated without having knowledge of pavement layer thicknesses. Two regression models were developed based on several thousand FWD deflection data to calculate SNeff of pavements and resilient modulus (MR) of their subgrades. Subgrades MR values together with traffic data were then used to calculate SNreq. Statistical analysis of deflection data indicated that Area under Pavement Profile (AUPP) and the deflection at distance of 60 cm from load center (D60) parameters showed to have strong correlation with SNeff and MR respectively. The determination coefficients of the two developed models were greater than those of previous models reported in the literature. The significant result of this study was to calculate SNeff and MR using the same deflection data. Finally, imple­mentation of the developed method was described in determining appropriate Maintenance and Repair (M&R) method at network level pavement management system

Evaluating fatigue behavior of asphalt binders and mixes containing Date Seed Ash

Fatigue is one of the most occurring distresses in asphalt pavements. Asphalt binder plays a critical role in fa­tigue behavior of asphalt mixes. Modelling and predicting fatigue behavior of binders will result in more fatigue resistant mixes. In this research, possibility of using Date Seed Ash alongside two commonly used additives (namely, a siliceous and a limestone) as bitumen modifier were investigated. Then, the influence of these additives on fatigue behavior of asphalt binders and mixes was investigated. Linear Amplitude Sweep (LAS) test was carried out and Viscoelastic Con­tinuum Damage (VECD) parameter was determined. In addition, Indirect Tensile Fatigue Test (ITFT) was performed on mixes containing these additives. Correlation equations were developed to link fatigue behavior of binders to those of mixes. The results showed acceptable agreement between binders and mixes fatigue testing results. In addition, with predicted models it was able to obtain the asphalt binders contribution to mixes fatigue resistance. However, in the case of ash modified samples, no good correlation was observed between fatigue behavior of binders and that of mixes

Optimizing the mix design of cold bitumen emulsion mixtures using response surface methodology

Cold mix asphalt (CMA) has been increasingly recognized as an important alternative worldwide. One of the common types of CMA is cold bitumen emulsion mixture (CBEM). In the present study, the optimization of CBEM has been investigated, to determine optimum proportions to gain suitable levels of both mechanical and volumetric properties. A central composite design (CCD) with response surface methodology (RSM) was applied to optimize the mix design parameters, namely bitumen emulsion content (BEC), pre-wetting water content (PWC) and curing temperature (CT). This work aimed to investigate the interaction effect between these parameters on the mechanical and volumetric properties of CBEMs. The indirect tensile stiffness modulus (ITSM) and indirect tensile strength (ITS) tests were performed to obtain the mechanical response while air voids and dry density were measured to obtain volumetric responses. The results indicate that the interaction of BEC, PWC and CT influences the mechanical properties of CBEM. However, the PWC tended to influence the volumetric properties more significantly than BEC. The individual effects of BEC and PWC are important, rather than simply total fluid content which is used in conventional mix design method. Also, the results show only limited variation in optimum mix design proportions (BEC and PWC) over a range of CT from 10oC to 30oC. The variation range for optimum BEC was 0.42% and 0.20% for PWC. Furthermore, the experimental results for the optimum mix design were corresponded well with model predictions. It was concluded that optimization using RSM is an effective approach for mix design of CBEMs

Properties of WMA–foam mixes based on major mechanical tests / Šiltai maišyto asfalto mišinių, gaminamų pagal putoto bitumo technologiją (WMA-Foam), savybės remiantis pagrindiniais mechaniniais bandymais

One of the main advantages of warm mix asphalt (WMA) used as an alternative to conventional hot mix asphalt (HMA), is to reduce mixing and compaction temperatures. This laboratory study was conducted with the aim of determining physical properties of WMA mixes produced using foam bitumen technology (WMA–Foam), while applying different mixing and compaction temperatures. The effect of laboratory compaction method on mix properties was also investigated. WMA–Foam mixes were produced, adding a soft bitumen to coarse aggregate particles at the first stage, then a hard bitumen, transformed into foam bitumen using a laboratory foam making device, was directly added to aggregates at the next stage. Compaction was performed separately applying both Marshall and gyratory compactors (GC) at different temperatures. Marshall Stability and void contents of the samples were determined as two major parameters for characterizing WMA–Foam mixes. Moisture susceptibility and rutting potential of WMA–Foam samples were evaluated using indirect tensile strength (ITS) and wheel tracking tests. In addition, separate samples were prepared, in which hydrated lime powder was added as an anti-stripping agent to improve adhesion properties of the mixes. Comparing the results of WMA–Foam mixes with control HMA of the same content, resulted in mixes with similar properties of the control HMA, with appreciably lower production and compaction temperatures of the former. It was also resulted that mixes compacted with gyratory compactor were less sensitive to temperature variations than those compacted with Marshall Hammer. Santrauka Pagrindinis šiltai maišyto asfalto mišinių privalumas, lyginant su įprastiniais karštai maišyto asfalto mišiniais, yra galimybė sumažinti asfalto mišinio maišymo ir tankinimo temperatūras. Šio laboratorinio tyrimo tikslas – nustatyti šiltai maišyto asfalto mišinių, gaminamų pagal putoto bitumo technologiją (WMA-Foam), fizines savybes taikant skirtingas maišymo ir tankinimo temperatūras. Taip pat buvo tirtas skirtingų laboratorinių tankinimo metodų poreikis asfalto mišinio savybėms. WMA-Foam technologijos mišiniai gaminti pirmame etape į stambiąsias mineralines medžiagas dedant minkštąjį bitumą, o kitame etape – kietajį bitumą specialiu laboratoriniu putojimo įrenginiu pavertus putotu bitumu dedant į pirmame etape paruoštas mineralines medžiagas. Tankinta atskirai Maršalo plūktuvu ir giratoriaus presu skirtingose mišinio temperatūrose. Maršalo bandinių pastovumas ir oro tuštumų skaičius buvo nustatyti kaip du pagrindiniai WMA-Foamtechnologijos mišinius charakterizuojantys parametrai. WMA-Foam technologijos bandinių jautrumas vandeniui ir atsparumas provėžų susidarymui buvo vertinti pagal netiesioginio tempimo jėgos ir rato riedėjimo vėžės nustatymo bandymus. Keletas bandinių papildomai buvo pagaminti su gesintosiomis kalkėmis, t. y. asfalto mišinio sukibimą gerinančiu priedu. Lyginant WMA-Foam technologijos ir karštai maišyto asfalto mišinių bandymų rezultatus nustatyta, kad identiškos sudėties WMA-Foam technologijos mišinių savybės yra panašios į karštai maišyto asfalto mišinių savybes, tačiau jos pasiekiamos pastebimai žemesnėse maišymo ir tankinimo temperatūrose. Taip pat nustatyta, kad asfalto mišinio bandiniai, pagaminti giratoriaus presu, buvo ne tokie jautrūs gamybos temperatūros kitimui, lyginant su bandiniais, pagamintais Maršalo plūktuvu. Reikšminiai žodžiai: WMA-Foam technologija, karštai maišyto asfalto mišinys, mišinio sudėtis, putotas bitumas, tankinimas, jautrumas vandeniui, provėžų susidarymas, netiesioginė tempimo jėga (angl. Indirect Tensile Strength–IT

The role of rejuvenating agents in cold recycled foam asphalt mixes

Cold-in-place asphalt recycling is one of the most commonly used methods of pavement rehabilitation. Using rejuvenating agents can activate the RAP binders and improve performance of cold recycled mixtures. In this study, waste cooking oil (WCO) and a combination of waste cooking oil and a soft asphalt binder (WCOSB) were used to recycle mixtures containing different amounts of Recycling Asphalt Pavement (RAP) materials. The WCOSB rejuvenator was mixed with cold RAP materials in different methods in order to investigate the effectiveness of the rejuvenating agents in recycled mixtures. Modified Lottman, Hamburg wheel tracking, four-point bending beam fatigue, and semi-circular bending fracture tests were conducted on the mixtures. Performance of WCOSB was better than that of WCO against moisture sensitivity. It was shown that WCO weakened the cohesiveness of the asphalt binder and reduced moisture resistance of the asphalt mixtures. Therefore, this material cannot be considered as an effective rejuvenating agent despite its positive rutting performance and cracking resistance in recycled mixes. Investigating the method of application of the rejuvenating agent, it was found that addition of the rejuvenator to RAP materials resulted in better cracking and moisture resistance of the recycled mixtures. This is despite its adverse effect of increasing rutting susceptibility of the recycled mixtures